Timely harvesting is a critical factor in seed production to decide the seed yield and quality. Seed lot performance depends on physiological and functional changes that occur at the time of anthesis until seeds are ready for harvest. Studies on pattern of seed development and maturation have superior effectiveness on production of quality seeds.
Malarkodi and Srimathi (2007) reported that days, symptoms and phases for seed growth and maturation differed with crop to crop and studies on seed maturation were necessary not only for individual species but its to locations also.
Harrington (1972) stated that in physiological maturity seed reach its dry weight at maximum and nutrient goes into seed from mother plant is stopped by breaking of vascular connection by abscission layer formation (
Eastin et al., 1973). In this study, prototype of seed development and maturation in horse gram was detected to fix the optimum time and symptoms of physiological maturity for harvesting of good quality seeds.
Changes in pod characteristics during seed development and maturation
Fresh weight of pod increased gradually and attains maximum of 6.903 g at 35 DAA. The fast growth of seed after fertilization to 35 DAA due to more uptake of water, nutrients and accumulation of photosynthates from source to sink which was increasing with seed maturity. Such results were also reported by Renugadevi
et al., (2006) in cluster bean and
Fakir et al., (2013) in
Dipogon lignosus. Moisture content of pod was higher (92.2 %) at 7 DAA and decreased gradually to 15.1% at 56 DAA (Table.1). McIlrath
et al., (1963) stated that water loss is considered as inherent phase of seed development and maturation and decreased due to dehydration and desiccation as opined by
Abdul-Baki and Anderson (1973). Similar decrease in fresh weight of pods was also reported by
Indira and Dharmalingam (1996) in fenugreek;
Gnyandev (2009) in chickpea;
Pushp et al., (2013) in groundnut;
Ragupathi et al., (2017) in proso millet;
Sridevi and Manonmani (2019) in proso millet and
Hirpara et al., (2020) in soybean.
Pod length was increased upto 4.76 cm at 35 DAA and thereafter slight decrease was observed in length due to drying. By reason of drying, the pod was shrink and it result that decreasing of length of pod from 42 DAA (4.43 cm) to 56 DAA (4.30 cm). Similar results were observed by
Deshmukh et al., (2011) in cowpea,
Krishnakumary (2012) in cowpea and
Sajjan et al., (2005) in okra. Pod weight was supported by increasing of pod length which attained the highest at 35 DAA (Table 1). Similar finding was also reported by
Das and Fakir (2014) in
Lablab purpureus. Maturation process leads with loss of water depending upon atmospheric condition.
Khattra and Singh (1995) also stated that dry matter accumulation with moisture loss is characteristic feature that observed during seed development and maturation. Decrease of pod moisture content was at faster rate is due to replacement of osmotic materials such as starch and other large molecule with low hydration capacity.
Ellis et al., (1987) discussed that harvest was delayed beyond optimum moisture content leads to decrease in viability and increasing of seedling abnormalities (Plate 1).
Physical changes in seed characteristics during seed development and maturation
Maximum fresh weight of seed was attained at 35 DAA and falls down of weight due to breakdown between source to sink and moisture content depeletion. Such results supported by
Murali et al., (2019) in French marigold. The weight reduction is also due to reduction of volatile substances in semi fluid state that might have escaped along with water as opined by
Rao and Rao (1975) and
Delouche (1973). Physiological maturity occurs commonly in seeds to reproductive capacity is recapture for following germination and its overlap by attainment of maximum dry weight where flow of nutrients from mother plant to seed is stopped was opined by
Harrington (1973). Seed dry weight is the main feature of seed maturation which maximized at 49 DAA (0.859 g/25 seeds) (Table 2). Synthesis and deposition of minerals like starch in endospermic tissue is a factor for increasing of seed dry weight. Duration of physiological maturation is the stage between fertilization and accumulation of maximum dry weight that results in maximization of seed and seedling quality characters. In last phase of horse gram (56 DAA), reduction in dry weight of pod and seed is due to exclusion of some amount of nutrients along with moisture elimination. Such result was obtained
Monalisa et al., (2018) in sesame. Seed moisture content was quite high at 7 DAA (89.3 %) which reduced significantly to 56 DAA (13.5 %) due to desiccation and dehydration. Such result was obtained in
Deepak et al., (2019) in rice. Pod and seed colour is the visual index of seed maturation. It was observed that pod colour changes from green group at 7 DAA to straw colour group at 49 DAA and the seed colour changes from green group at 7 DAA to brown group at 49 DAA (Plate 1). It could be seen that the process of physiological maturation in seeds was accompanied by visible changes in the external appearance and coloration of the pods and seeds, thus corroborating the results of
Castro et al., (2008).
Physiological changes in seed characteristics during seed development and maturation
Germination is the important indicator of seed quality (
Khan, 1977) where the final produce is seed, which is for regeneration capacity. In horse gram, seeds from 7 DAA to 28 DAA incapable to germinate due to the immature embryo, although the seeds from 35 DAA attained a germination of 47% which increased maximum at 49 DAA (94%) but after that it decreased to 90% at 56 DAA (Table 3).
Germination percent was maximum at 49 DAA might be due to attainment of potentiality for reproduction of miniature plant.
Woodstock and Combs (1964) reported shoot length and root length is a measure of vigour which reveals the seed performance under environmental conditions. Seedling length was maximum in seeds from 49 DAA. Dry matter production increased gradually from 35 DAA to 49 DAA thereafter dry matter decreased slightly due to the development of inbuilt mechanism that involved in the disorganization of cell organelles after physiological maturity. Similar finding was also reported in peas by
Mathews (1973) and in yard long bean by
Sakthivel et al., 2023. The computed vigour index was maximum in 49 DAA which was positively correlated with the dry weight of seed. Similar results were also reported in
Suresh Babu et al., (2003) in brinjal;
Natarajan and Srimathi (2008) in petunia and
Sundareswaran et al., (2011) in bhendi.